This project examines the synaptic connections between primary neurons which make up trigeminal and spinal nerves on one hand and the neurons of the medullary and spinal dorsal horns on the other hand especially those in the substantia gelatinosa of Rolando. This project also considers the form, synaptic connections and function of the neurons of the dorsal horn as well as their pathological responses to peripheral nerve injuries. These studies employ electron microscopy, the Golgi method, degeneration techniques and the use of intraneuronal markers such as horseradish peroxidase. The goals of these studies are to delineate trigeminal and spinal pain-temperature pathways and to broaden our understanding of oral-facial sensation.